What were 3 major mistakes made by Hitler during world war 2?

Several mistakes have been suggested:

1. He did not demand the entry of Spain on the side of the Axis.
2. He stopped air superiority bombing in favor of terror bombing in England.
3. He delayed his invasion of the Soviet Union to invade the Balkans and help out Italy in its failed invasion of Greece.
4. He underestimated the manpower and resiliency of the Soviet Union (a big mistake).
5. He diverted assets from the drive on Moscow in 1941 and did not take it.
6. In the 1942 offensive he split his forces in an attempt to take two strategic objectives: Stalingrad and the Caucasus. He made the problem worse by diverting forces from Stalingrad to the Caucasus.
7. He refused to let his encircled 6th army try to break out of Stalingrad.
8. He did not require Japan to declare war on USSR in return for Germany declaring war on the US (another big mistake).
9. He did not suspect that the Western powers had cracked his communication codes until it was too late.
10. He was late in sending sufficient troops soon enough to Rommel in Africa. When he did send large numbers, it was too late and he lost them all.
11. He often did not follow the advice of his General Staff, particularly in regard to ceding territory to gain room for maneuver.
12. He did not commit all his available panzer divisions to the defense of Normandy quickly enough.
13. He did not put Germany on a total war economy until 1942 or even 1943.
14. He did not put enough resources into the development of an atomic bomb.
15. He chose major allies that were of little use to him.